Method of making methylene bisphosphorus esters



nited SIRS Patented Dec; 19, 1951 This invention relates to methods forpreparing bis(S- [dialkoxyphosphinyl]mercapto)-methanes andbis(S-[dialkoxyphosphinothioyl]mercapto)-methanes by the reaction of ametallic salt of a thioor dithiophosphoric acid, with dibromomethane orbromochloromethane It aims to provide a novel method for the preparationof the indictated-compounds, characterized by simplicity of operation,short reaction times and high yields of the desired end products.

In our copending application Serial Number 597,886, filed July 16, 1956,now Patent No. 2,873,228, of which this application is acontinuation-in-part, we have described and claimed the compoundbis(S-[diethoxyphosphinothioyl]mercapto)-methane as an extremely activeinsecticide. This compound is one of a class of compounds having thegeneral formula Where X is oxygen or sulfur and R and R are organicradicals.

According to the instant invention, such compounds are prepared byreacting a soluble salt of a compound of the formula II R -PS-cationwhere X is oxygen or sulfur and R and R are organic radicals, with areactant of the class consisting of dibromomethane andbromochloromethane. The reaction is carried out by dissolving the saltinan appropriate solvent, adding a mol of the dihalomethane to two molarequivalents of the metal or other saltand heating the mixture untilreaction is complete, with the formation of the desired ester andhalide.

Surprisingly enough the reaction will not occur unless one or both ofthe halogens is bromine; dichloromethane is substantially unreactedunder substantially identical conditions, although 1,2 dichloroethanewill react.

In the preferred process of this invention, the thiophosphoric acid isneutralized to a'pH between 6 and 8 with a dilute aqueous alkali, e.g.,NaOH, KOH, NH OH, Ca(OH) or an alkaline amine. bromochloromethane isthen added over a short period of time and the reaction mixture isheated for two or more hours until the reaction is complete. Theprecipitated product, generally .an oil, is separated from the aqueoussalt solution by decantation, and is then filtered, washed and dried.

Alternately, the product may be made in an organic solvent such as alower alcohol, dioxane, pyridine or similar medium which will not reactwith the methylene halide. However, results are not as satisfactory aswith the preferred aqueous medium. Separation of the product issubstantially more difficult, and the reaction times are somewhatlonger.

The following examples illustrate the methods of this invention. Thereare, of course, many modifications which may be successfully employed bythose skilled in Dibromomethane or the art, and which do'not depart fromthe scope of the invention as defined in the claims.

EXAMPLE 1 Preparation of bis(S-[diethoxyphosphinothioyl]mercapt0)-methane Two molar equivalents of O,O-diethyl hydrogenphosphorodithioate were dissolved in sufiicient ethanol to give a fourmolar solution. A solution of potassium hydroxide in ethanol was addedslowly, the temperature 15 maintained below 50" during the addition,until the pH of the solution was approximately 7.0. To the neutralsolution was added 1 molar equivalent of dibromomethane and the mixturewas heated under reflux for six hours. The precipitated solid potassiumbromide was filtered oh, and the filtrate was concentrated under vacuum.The residue after removing the solvent was diluted with ether, thesolution washed with two volumes of water and the ethereal layer dried.The dried solution was concentrated under vacuum to give 0.74 molarequivalent of a colorless liquid having an n D 1.5315. Analysis: Calcd.for C H O P S P 16.13, S 33.34; P/S ratio 0.50. Found: P 16.04, S 33.72;P/S ratio 0.51. When the dibromomethane in the above procedure wasreplaced by chlorobromomethane, 0.78 molar equivalent of colorlessliquid having an n -D 1.5285 was obtained.

Bio-assay, and chemical analysis, indicated the two prodnets to beidentical. Analysis: Calcd. for C H O P S I P 16.13, S 33.34; P/S 0.50.Found: P 16.25, S 33.63;

5 P/S ratio 0.50.

3 EXAMPLE Bis(S- [dicyclohexyloxyphosphinothioyl] mercapto) methane s sI OuH1rOIl SCHgS-id-O-C H nHn o i1 Two molar equivalents of0,0-dicyclohexyl hydrogen methane. The mixture was heated under refluxfor 2.5.

hours and the reaction mixture treated as described in Example 1 to give0.40 molar equivalent of a viscous orange-brown liquid having an 71 B1.5290. Analysis: Calcd. for C H O P S P 10.32, S 21.34; P/S ratio 0.50.Found: P 10.45, S 21.29; P/S ratio 0.51. 1

EXAMPLE 3 Bis(S- [diethoxyphosphinyl] mercapto -methane II II o,H50-1=s-0H2-sP-o can '60 O CaHs .O CaHs To an ethanolic solution containing 2molar equivalents of sodium 0,0-diethylphosphorothiolate, prepared byreaction of elemental sulfur with 0,0-diethyl phosphite according to theprocedure of Fiszer, et al. (Chem.

Abstracts, 49, 3 86 [1955]), was added one molar equivalent ofdibromomethane. The reaction mixture was heated under reflux for sixhours and the product re- 5 covered as described in'Exarnple 1, to give0.23 molar equivalent of dark red liquid having an n D 1.4678. Analysis:Calcd. for C H O P S P 17.58, S 18.20; P/S ratio 1.00. Found: P 19.80, S20.40; P/S ratio 1.00. The following products were prepared followingthe ethanolic potassium hydroxide, the temperature main 3 generalprocedure outlined in Example 1 to indicate that the substituents, R andR can be alkyl, cycloalkyl, aryl and chloraryl.

percent NaOH which brought the pH to 8. Three sue cessive batches gaveyields of 79.5 percent, 78.6 percent and 7 8.6 percent of theoretical,respectively. The miti- TABLE 1.PHOSPHINOTHIOYL- ANDPHOSPHINYLMEROAPTOMETHANES Compound Analysis 7125]) R R X Theory FoundMethyl s 1.5247 P18.89 P-17.39 Ethyl S 1.5315 P-lts. 13 Pl6.04 Ethyl.-.0 1. 4678 1 -17.5s Pl9. so n-Prop s 1. 5220 r-14.os P-14.04 Isopropgl S1.5l63 P-l4.08 P-14.05 n-But s 1. 5110 P-12.4o P12.18 Isobutyl s 1. sassP-l2.49 Pl2. 1s Ethyl/isopropyl 1:1). S 1.525s Pl5.04 1 15.o9Ethyl/isopropyl 3:1 S 1. 5298 Pl5.57 P-15.60 Cyclohexyl S 1.5290 P-l0.32 Pl0.49 Ph s 1. 5722 P-10.74 Pl0.83 s 1.5805 P- 8.67 P- 8.51 Et S1.5350 1 12.s7 Pl2.47

Other organic radicals, such as aralkyl and alkaryl cidal activity wassomewhat better than that of laboratory hydrocarbon radicals, can alsobe substituted. prepared maiterial. b d fi h d The speci c examples cane mo i ed wit out apart- EXAMPLE 4 ing from the scope of the inventionwhich is set forth in Preparation ofbis(S[diethoxyphosphinothioyl]mercapth 1 i to)-methane. 279 grams (oneand one-half mols) of Wh i l i d i 0,0-diethyl hydrogenphosphorodithioate were dissolved 1, Th h d for preparing a compound of[hg in the 20 percent solution of 85.5 grams (1.5 mols) of f l KOH togive a solution with a pH of 6.5. The ethanol was removed and replacedwith 200 millimeters of dioxane. 130.5 grams of dibromomethane (0.7 mol)were ROP-'S'-CHZ-S P-OR added and the solution was refluxed for fourhours. The mixture was cooled; the resultant precipitate was filtered,where X i l d f th group consisting of oxygen and the Olly PrPductrecovered- The Ymld was and sulfur and R and R are organic radicalsselected Cent of theoreucalfrom the group consisting of alkyl,cycloalkyl, aryl and EXAMPLE 5 40 chloraryl which comprises heatingabout 1 mol of a com- E l s was repeated b h dib h was pound of theclass consisting of dibromomethane and replaged by bromochloromethaneThe was ChlOl'ObfOIIlOIllfithfll'le With alJOLli. 2 mols Of a salt Of apercent of h i L thiophosphoric acid of the formula When Examples 4 and5 were repeated using dichloromethane, the products were obtained invery much lower R1 1, S cation yield, and the refractive index of thematerial was substantially lower than that obtained with dibromomethanef bromochlommethane, mdlcatmg a dlfierent where X is selected from thegroup consisting of oxygen stitutlon. and sulfur and R and R are organicradicals selected EXAMPLE 6 from the group consisting of alkyl,cycloalkyl, aryl and Aqueous preparation f i (5 di h h hi hi chloraryl,in an inert solvent for the salt, until reaction yl]mercapto)-methane.200 .lbs. of 0,0-diethylphos- 18 complete, and separatms the halideformed f m t e phorodithioate were placed in a reaction vessel and newresultant blsmethylene p f tralized with 174 lbs. of 25 percent aqueouscaustic The mfithcd P p a compound of the soda; the pH was brought backfrom 9 to 8 by adding formula 9 more lbs. of the acid; temperature rosefrom about H N 20 C. to 32 C. during the addition. The batch was heatedto 50 C. and 88 lbs. of dibromomethane were R10 P s CHTS P added over. aperiod of one-half hour during which time the temperature rose to The ithan where X is selected from the group consisting of oxygen heafed forthree hours at 80-856 at Whlch tlme and sulfur and R and R are organicradicals selected action appeared complete. The batch was washed by fromthe group consisting of alkyl, cycloalkyl, aryl and decantation, firstw1th 45 gallons of water and then with chloraryl which comprises heatingabout 1 mol of a g l f 0f Product was fi t0 remove compound of the classconsisting of dibromomethane 1mpur1t1es, reslurned with water andallowed to settle. and chlorobmmomethane with about 2 mols of a salt Thei y liquid was drawn it 163 of a thiophosphoric acid of the formularesenting a 75 percent yield. The m1t1c1dal act1v1ty of this batch wascompared with a standard made in the H laboratory, and was found to besomewhat superior. R 0PS-cation' EXAMPLE 7 R The process of Example 6was repeated substituting where X is selected from the group consistingof oxygen 70 lbs. of brornochloromethane for the 88 pounds of diandsulfur and R and R are organic radicals selected brornomethane. In thiscase, 200 lbs. of the 0,0-diethylfrom the group consisting of alkyl,cycloalkyl, aryl and chloraryl in an aqueous medium, until reaction iscomphosphorodithioate were neutralized with 167 lbs. of 25 plete, andseparating the halide formed from the resultant bismethylene compound.

3. The method of preparingbis(S-[diethoxyphosphinothioyl]mercapto)-methane which comprises heatingabout 1 mol of a compound of the class consisting of dibromomethane andbromochloromethane with about 2 mols of a salt of 0,0-diethyl hydrogenphosphorodithioate in an inert solvent for the salt, until reaction iscomplete, and separating the halide formed from the resultantbismethylene compound.

4. The method of preparing bis(S-[diethoxyphosphinothioyl]mercapto)-methane which comprises heating about 1 mol of a compound of the classconsisting of dibromomethane and bromochloromethane with about 2 mols ofa salt of 0,0-diethy1 hydrogen phosphorodithioate in an 15 aqueousmedium, until reaction is'complete, and separating the halide formedfrom the resultant bismethylene compound.

References Cited in the file of this patent UNITED STATES PATENTS OTHERREFERENCES Clark et al.: J. Agr. Food Chem, 3, 834-836 (1955).

1. THE METHOD FOR PREPARING A COMPOUND OF THE FORMULA